Television receiving method and apparatus



1936 L. DE FOREST TELEVISION RECEIVING METHOD AND APPARATUS 2 Sheets-Sheet 1 Filed April 24, 1951 Jam 7 1936. L. DE FOREST TELEVISION RECEIVING METHOD AND APPARATUS 2 Sheets-Sheet 2 Filed April 24, 1931 Patented Jan. 7, 1936 UNITED STATES PATENT OFFICE I mvIBION RECEIVING METHOD AND Lee de Forest, Hollywood, cum, designer to American Television Laboratories, Inc., a corporation of Delaware This invention has to do in. a general way with the art of television and relates more particularly to improved methods for receiving televised pictures and images.

It is well known to those familiar with the art that images can be converted into electrical impulse modulations which may be transmitted by radio or by wire and received at distant points, where, through the medium of so-called television receiving apparatus, they can be converted into images corresponding to the transmitted images. The reproduction of the images at the receiving station is generally accomplished by means of a pulsating neon light associated with a scanning l5 disk, and since thequantity of light available is small, the reproduced image is very dim and is incapable of magnification. It, therefore, becomes a primary object of this invention to produce a method or methods of the class described whereby the televised images may be reproduced with light of sufficient intensity to permit their magnification, and if desired, their projection onto a much larger screen area than has heretofore been possible. v

2 Pursuant to the attainment of this object the present invention contemplates the recording of the televised image upon the suitably prepared surface of a plate, strip or film of the motion picture type, and, if desired, the projection of these pictures bymeans of a projector oi the type such as is ordinarily used in connection with motion pictures. By this method I am able to reproduce the received televised images with a much brighter light and may project them over a much greater screen-area than has heretofore been possible.

Furthermore this'methodmakes possible the projection of the received televised picture through a projector similar to that used in motion picture theatres whereby the greatly enlarged screen image of the picture is projected on a screen located at a long distance from the projector so that it may be seen by a large audience in a theatre.

Iniaccomplishing this method I employ with the 45 usual television signal receiver, whether these signals be received by radio or by wire, an equivalent of the ordinary television receiver. scanning disk so designed that the received image is first impressed or delineated upon a strip of motion 50 picture film which is immediately thereafter passed through a picture projection machine in all respects similar to those used in the motion picture theatres at the present time, whereby the received and recorded televised picture is pro- 5 jected in the manner customary to motion picceiving and sound reproducing equipment is used,

it is to be understood that while this method will 5 be described with particular reference to motion picture film, it may be employed in any telephoto work for recording a televised image upon the properly coated surface of any suitable material. 10

In connection with this process my invention also contemplates the reproduction of sound in connection with the projected picture. In the event the televised images coming from the transmitting station have their source in a motion pic- 15 ture film, it will be apparent that the film. may be of a type ordinarily used in talking pictures which carries a so-called sound track, and in this event the sound track is reproduced upon the film at the receiving station, a film of this char- 2 acter may be passed through the ordinary type of photo-electric sound reproducing apparatus so that the sound is reproduced in synchronism with the projected picture. Another method is to broadcast the sound record at the transmitting :5 station running the record through thetransmitterso that the sound is transmitted at a time interval behind" the picture such that these impulses received at the receiver will be reproduced in synchronism with the projected picture. 30 Where the televised image is that of actual action which is taking place at the transmitting station, it will be seen that if the usual type of radio rethe sound will precede the picture by several seconds. Where it is desirable, as is usually the case, to transmit the sound or voice simultaneously and in synohronism with the picture from the transmitter, this difiicuity can be overcome in one of several ways, and it is a further object of this invention to provide a method or an apparatus whereby the sound coming from the transmitting station may be reproduced simultaneously and in synchronism with the projected televised picture. 4,5

The accompanying drawings illustrate a certain form of apparatus which I have invented whereby the methods or operations contemplated by this invention are made possible.

Referring to the drawings- Fig. 1 is a more or less diagrammatic view showing one form of apparatus contemplated by this invention;

.Fig. an a plan view showing a part of the picture recordingapp ratus; 56

Fig. 3 is an enlarged sectional elevation which may be'considered as having been taken in a plane represented by the line 3-8 in Fig. 2;

Fig. 4 is another diagrammatic view illustrating a modified form of apparatus for carrying out the method contemplated by this invention.

More particularly describing the invention as herein illustrated, reference numeral ll indicates a strip of motion picture film which may be of the ordinary celluloid base or may be of other suitable diaphanous material, such as cellophane, carrying along its two margins the two standard film perforations. This film is specially prepared before it passes through the television scanning or reproducing apparatus so as to carry on one face a uniformly blackened or opaque surface. This blackened surface may be one of several suitable materials, for example, it may be formed by previously uniformly exposing, developing and fixing one of any number of standard motion picture film emulsions. Further the blackened surface may be composed of conducting or semiconducting ink or graphitized pigment, evenly I and uniformly applied to the surface of the film base. The surface may be dry or moistened.

The film ll prepared in this manner is shown as coming from a magazine reel l2 and passing over suitable guide rollers is to a block I4 composed of insulating material and provided with a curved strip l5 of conducting material which is mounted in and suitably secured to the block M. In passing over the block H the film passes be-v .neath the periphery of what I may term a scan- .ning disk It which is provided with a plurality of discharge points I! situated so as to pass im-v mediately over the top edge of the conducto strip l5.

The conductor strip I5 is embodied in the block l4 so that its upper edge is fiush with the top surface of the block and it will be observed that this block is supported by a bracket I'Ia which is ad- Ju'stableby means of a screw I8 and a worm unit l9 so as to vary the distance between the edge of the conductor strip I5 and the plane described by the points II.

The scanning disk I6 is mounted through the medium of a hub upon an upright shaft 2| and ,is adapted to be driven at a high rate of speed in any suitable manner such as by means of the speed increasing gears 22 and the synchronous motor 23. It is to be understood that the present invention is not concerned with the means for synchronizing the receiver scanning disk with the transmitter scanning disk, and any of the well known means employed for this purpose may be used herein.

The points H are situated on equal radii of .the disk l6 and are equally spaced apart a peripheral distance which is equal to the width of the picture carrying area of the film H. In other words, for the standard type of motion picture film the needle points on the lower surface of the scanning disk are separated by a distance of approximately of an inch. The conductor plate 15 is curved as mentioned above with a radius of curvature slightly less than the scanning disk l6 so that during the rotation of the scanning disk one of the points I1 is always above a. portion of the conductor strip [5. g

The points [1 which'may be hereinafter referred to as discharge points, are preferably constructed in the manner shown in Fig. 3 where the points are shown as comprising the lower end portions of fine pieces of conducting material such as platinum wire indicated by reference numeral I jector 52.

25. This wire is contained within a sleeve of insulating material such as glass, indicated at 21, and the upper end of each of the conducting wires or needle points is connected by means of a conductor 28 to a corresponding segment 29 of a com- 5 mutator 30 which is mounted upon the upper face of the scanning disk IS. A single brush 3! is mounted upon a bracket 82 so arranged as to make contact with that commutator segment which is connected at any moment to the discharge point which is at that time traversing the film directly over the conductor strip it.

The brush 3| is connected by means of a conductor 34 with one terminal of a high frequency transformer shown at 35. The other 15 terminal of the high frequency coil is connected either directly or through a conductor 36 with a conductor 31, making contact with a pole 31' on the conductor strip l5.

Reference numeral 38 indicates an oscillating 2o audion with one type of oscillation or feed back circuit connecting the three elements of the audion. Such an oscillating system, for example, was shown in my United States Patent No. 1,507,016 issued on September 2, 1924. Reference numeral 40 indicates the source of high voltage for supplying circuit to the plate electrode of the audion. 42 indicates the choke coil and 43' the primary of the high frequency transformer which is inductively associated with the secondary coil referred to above. The inductive relationship between the two coils 35 and 43 may be varied as shown, or the capacity 36 of the conductor 31 in the secondary circuit may be variable. By such means I am able to 35 accurately control the normal amount of high frequency energy passing from the oscillating audion system to the points of the scanning disk. Ordinarily when the oscillating system 38 isin operation the needle or discharge points of the scanning disk passing in rapid succession over the blackened surface of the advancing film ll acts to effect the opacity of the surface by either removing or rearranging the individual particles forming the coated surface through the medium l of chemical action, burning, heat, electrical or magnetic action.

In Fig. 1 I have shown a method of grid modulation of the oscillating audion 38 wherein the secondary 44 of the transformer 45 is connected between the grid 46 and the filament 41 of the oscillator in a manner such as to transfer the incoming televised energy which is received from an output terminal 48 of a television receiver 49 which embodies the standard television rethe sprocket 50 the film passes over the upper or pull down sprocket 5| of a motion picture pro- Reference numeral 53 indicates the usual aperture plate of the motion picture pro-- jector, such aperture plate being associated with an are light 55, the usual parabolic reflector 56 and the condensing lens 51. Reference numeral I 58 indicates an intermittent sprocket and 59 the 76 lower sprocket of the projector. Reference numeral 60 indicates the objective lens of the proiector in frontof which the rotating shutter Si is located. Reference numeral 12 indicates the distant screen on which the image is projected and reference numeral 63 indicates the photo electric sound transferring apparatus ordinarily used in connection with the film method of reproducing sound.

It will now be seen that by means of the apparatus so far described, the blackened surface of the specially prepared film H as it is propelled over the conductor strip l6 and below the periphery of the scanning disk I! by means of the -sprocket 50, will be attacked and modified by the field of force or electrical discharge created between the rapidly moving points I! on the scanning disk and the conductor strip l5 so that the modulated high frequency discharge passing between the needle points of the scanning disk to the film and directed at the conductor stip will reproduce in black, gray or white -the outlines and graduations of the pictures which are being televised at the distant transmitter of the television system.

This system just described might be more specifically defined as one in which a coated surface is electrically etched by subjecting successive portions of the surface to the action of an electrostatic discharge which is modulated by impulses received in a television transmitter and where an etching system of this character is employed, I consider it important to provide some means for blowing away any dust, ashes or fine particles of emulsion which might otherwise accumulate and interfere with the progressive operation of the device. Reference numeral 65 (Fig. 2) indicates a blower which may be provided for this purpose.

It is to be understood that my invention is not necessarily confined to a process wherein material is actually removed from the coated surface, but that it might embody any process wherein a change in the opacity of the coating is eifected by exposing successive portions of the coating to a modulated field of force which is electrically controlled by impulses received in a television receiver.

For example the original unetched or unexposed surface may embody a thin uniform application of some readily oxidizable chemical substance, preferably light colored and translucent. It is well known that a point electric discharge, whether of high frequency or unidirectional, ozonizes theiair in its immediate vicinity. This freshly ozonized air, at the point of the fine wire or discharge point on the scanning disk will instantly oxidize, more or less, the surface application mentioned above, rendering it more or less opaque in proportion to the intensity of the electrical potential existing between the point and the strip at that instant. It will be understood that the chemical action may be the reverse of the above, where the transparency of an opaque surface is affected by the varying ozonizing action at the discharge point. I also contemplate by my invention the use of a material which is similarly affected by a magnetic field and under these circumstances the discharge points will be replaced with miniature electromagnets which will create magnetic fields of varying flux density while traversing the surface.

In Fig. 2, reference numeral 66 indicates one manner in which the opaque surface of the film may be prepared, and reference numeral 61 indicates the manner in which the film appears after it has been subjected to the above described process.

As was pointed out in the fore part of the specification, this invention contemplates the re- 5 production of sound in connection with theprojection of the pictures, and such sound might be reproduced by impressing upon one edge 68 of the film a sound track 89 which corresponds to the sound track on the motion picture film at 10 the transmitting station, in the event the transmitted impulses originate from motion picture film. It is in connection with a film of this nature that I propose to use the photoelectric reproducing unit 63. The unit 63, it will be 011- is served from Fig. 1, is connected to an audio amplifier 10 which in turn is connected through a switch H with a power amplifier 12a associated with a loud speaker 13 which is situated behind the screen 12.

In the event the picture recorded on the film il corresponds to images of actual action which is occurring before the scanning disk of the television transmitter, and in the event sound is being broadcast in connection with such action by 25,

means of the usual radio broadcasting equipment, it is necessary to provide radio receiving means in connection with which sound delaying means must be provided so that the sound is finally reproduced simultaneously and in syn- 30 chronism with the projected pictures. As pointed out above, in securing this delay in the reproduction of the sound, I may utilize between the detector of the radio receiver which is bringing in the sound from the distant televised screen and so the loud speaker located behind the screen of the receiving station, one of the types of delayed circuits well known in the telephone art, or I may employ an apparatus such as is indicated generally by reference numeral 74 in Fig. 1. This 40 apparatus comprises the usual receiver 15 which is connected with the antenna i5 and in which the output is connected with an audio amplifier Ti which in turn is connected with aloud speaker head 78. This head, instead of being associated 45 with the usual type of diaphragm has its armature 19 connected with a long coiled wire 38 which may be composed of steel or bronze, and which has its other end connected with an armature 3! of a pick-up head 82. This head is shown 50 as being connected through a switch 83 with the power amplifier 12a which in turn'is connected with the loud speaker 73. By means of the coiled wire I am able to obtain by purely mechanical means almost any desired lapse of time between 55 the application of the sound impulses at the armature 19 and the taking off of such impulses at the armature 8!. This time lapse depends upon the mechanical characteristics of the transmitting wire, that is its overall length, its unit 0 mass, its state of tension, etc. I have found that by such means it is not difilcult to introduce the desired three or four seconds lag between the receipt of the sound impulse from the distant transmitting station and its reproduction in the loud as the blackened exposed photographic surface of the type referred to above. In other words, I have found that it is often desirable to employ a less expensive method wherein a single comparatively short strip of endless film or its equivalent is employed as the medium for receiving and carrying the picture record.

In Fig. .4 I show a preferred form of apparatus which may be used in carrying out this last mentioned method. In this figure reference numeral l6 indicates a scanning disk of the type described above and reference numeral I4 a guide block which contains the conductor strip IS. The scanning disk I6 is provided with discharge or needle points H, such points being electrically energized through a conducting system similar to that described in connection with Fig. 1,

which includes a conductor 34' and the conductor strip I being energized by a conductor 31. Reference numeral ll indicates an endless film which is coated by a method similar to one of the well known processes employed in printing, for facing one surface of paper or fabric with a uniform coating of ink or coloring material. The freshly prepared opaque surface of the looped film passes below a driven sprocket 90 and is drawn over the block [4' by means of a sprocket 9|. After leaving the sprocket 9| the passes through the projector indicated generally at 92 from which it is led over guide rollers 93, 93a and 93b for carrying it out of the plane of the projecting lens to a driven sprocket 94 from which it passes through an inking device indicated at 95 and past a flattened nozzle 96 where it may be subjected to a stream of heated ,1 or ozonizedair for drying the ink. The film then [passes between blotting rollers 91, being drawn "'"jtherethrough by means of a sprocketaSB, after which it is brought over guide rollers 9a, 99b

described in the fore part of the specification,

although it has one disadvantage in that it is impossible, through the use of this procedure, to form a permanent record of the televised picture.

I do not deem it essential in this specification to in any wise describe the television transmitter which may be any one of several well known types, for example one whereby motion picture film is passed in front of the televisor scanning disk and the outlines of the pictures on the film transmitted by means of a photo electric cell into variations of electric current which when suitably amplified are caused to modulate the high frequency energy radiated from the electrical transmitter. I have shown and described above means whereby a picture may be reproduced on film similar to the picture at a distant transmitter and immediately thereafter projected upon a motion picture screen located near the receiver. Such means may also be employed for reproducing or forming pictures of actual action which occurs at the transmitting station and in both instances I have shown means whereby sound originating at the transmitter may be reproduced at the receiver in synchronism with the projected image.

Many other modifications and changes in details will occur to those skilled in the art without departing from the spirit and scope of my invention as defined in the appended claims; but having now set forth the object and nature of 5 my invention and having shown and described structures embodying the principles thereof and illustrating the method employed in accordance therewith, what I claim as new and useful'and of my own invention and desire to secure by 10 Letters Patent, is:

1. The method of receiving television signals which comprises electrically imposing a patent image of the received electrically transmitted pictures on a moving film in a two-dimensional pattern through the medium of the electric discharge and immediately passing the film through a motion picture projector at motion picture speed of travel of the film so that the receipt of the picture and the projection thereof are substantially coincident.

2. The method of receiving television signals which comprises subjecting a moving film to electrical influence actuated by, in accordance with, and at the time of receipt of the electrically transmitted pictures to thereby impose a patent image of the pictures transmitted on the film in a two-dimensional pattern and immediately passing the film through a motion picture projector at motion-picture speed of travel of the film so that thereceipt of the picture and the projection thereof are substantially coincident.

3. An apparatus for producing motion pictures from televised images embodying: a conductor strip, a disc rotatably mounted in spaced relation with said conductor strip, a plurality of angularly spaced discharge points mounted in said disc in opposed relation with said conductor strip, a commutator on said disc having segments corresponding withand connected to said discharge points, a brush associated'with said commutator and arranged to engage each segment as the corresponding discharge point passes the conductor strip, a record strip comprising a transparent base and a volatile opaque'coating means for ad- (5 vancing said record strip transversely through the space between the conductor strip and the disc, and means for energizing the brush and the conductor strip from a television receiver, a motion picture projector, and means for feeding the record strip to the projector directly from said advancing means.

4. An apparatus for producing motion pictures from televised images embodying a conductor strip, a disc rotatably mounted in spaced rela- 65 tion with said conductor strip, a plurality of angularly spaced discharge points mounted in said disc in opposed relation with said conductor strip, a commutator on said disc having segments corresponding with and connected to said discharge points, a brush associated with said commutator and arranged to engage each segment as the corresponding discharge point passes the conductor strip, a record strip comprising a transparent base and a volatile opaque coating means for advancing said record strip transversely through the space between the conductor strip and the disc, and means for energizing the brush and the conductor strip from a television receiver, said discharge points being spaced apart (0 at a distance corresponding to the width of said coated film, a motion picture projector, and means for feeding the record strip to the projector directly from said advancing means.

LEE or: FOREST. in 

